Xiao Weixiong, Bai Shixun, Gao Shengwu, Liu Jiahui, Wei Pengzhi
Department of Petroleum Engineering, School of Petroleum, China University of Petroleum - Beijing at Karamay, Xinjiang 834000, China.
ACS Omega. 2025 Jul 23;10(30):33079-33089. doi: 10.1021/acsomega.5c02523. eCollection 2025 Aug 5.
Clay minerals in oil and gas fields are prone to swelling, impacting wellbore stability and causing difficulties in water injection. Quaternary ammonium type cationic antiswelling agents have become important clay swelling inhibitors due to their electrostatic adsorption capabilities. Quantum mechanical density functional theory (DFT) calculations show that the local charges of quaternary ammonium and ethylene groups can be adjusted by inserting different functional groups into the molecule. However, the impact of the molecular charge distribution on the antiswelling effect has not been fully revealed. This study tests 21 surfactants and polymers based on vinylbenzyltrimethylammonium, methyl ester trimethylammonium, and amido trimethylammonium structures through functional group insertion using quantum mechanics calculations (QM) and molecular dynamics simulations (MD). The correlation between charge distribution and changes in montmorillonite layer spacing is explored. By adjusting the molecular structure, a series of charge distributions are obtained to evaluate their impact on antiswelling performance. The results show that the partial charge on the α-C and the β-CH had the most significant impact on the antiswelling ability of the agent, with Spearman coefficients as high as -0.431 and -0.434, respectively, while the charge on the nitrogen atom had a weaker effect. Polar functional groups such as amido groups exhibit strong antiswelling properties, whereas hydrophobic functional groups are less effective. This study provides a theoretical basis for the molecular design of highly efficient antiswelling agents, which is of great significance for the time- and cost-efficient selection and development of antiswelling agents for water-sensitive reservoirs.
油气田中的黏土矿物易于膨胀，影响井筒稳定性并导致注水困难。季铵型阳离子防膨剂因其静电吸附能力而成为重要的黏土膨胀抑制剂。量子力学密度泛函理论（DFT）计算表明，通过在分子中插入不同的官能团，可以调节季铵基和乙烯基的局部电荷。然而，分子电荷分布对防膨效果的影响尚未完全揭示。本研究通过量子力学计算（QM）和分子动力学模拟（MD），基于乙烯基苄基三甲基铵、甲酯三甲基铵和酰胺基三甲基铵结构，通过官能团插入测试了21种表面活性剂和聚合物。探索了电荷分布与蒙脱石层间距变化之间的相关性。通过调整分子结构，获得了一系列电荷分布，以评估它们对防膨性能的影响。结果表明，α-C和β-CH上的部分电荷对防膨剂的防膨能力影响最为显著，斯皮尔曼系数分别高达-0.431和-0.434，而氮原子上的电荷影响较弱。酰胺基等极性官能团表现出较强的防膨性能，而疏水官能团效果较差。本研究为高效防膨剂的分子设计提供了理论依据，对水敏油藏防膨剂的高效、低成本筛选与开发具有重要意义。
